1. Field of the Invention
The present invention relates to compositions used in permanent hair waving processes. More particularly, the present invention relates to hair treatment compositions that improve the styling and reshaping of hair using a cold permanent hair waving process.
2. Description of the Prior Art
Hair is made up of a fibrous protein called keratin. The shape and stability of the structure of this protein is provided by three interactions; (1) covalent bonding of cystine cross-linkages; (2) hydrogen bonding; and (3) salt linkages. The disulfide bonds in cystine are the strongest of these stabilizing forces.
To change the natural shape of hair, various treatments have been devised. One such treatment is permanent waving of hair, which can be used to either increase or decrease the amount of curl in hair. Permanent waving of hair may be performed using different types of treatments. One such treatment is heat waving, which facilitates the breakage of the disulfide bonds by applying heat in conjunction with alkali, or a combination of an alkali and a sulfite reducing agent. However, the heat treatment and chemicals involved tend to weaken the hair fibers and most of the reactions are irreversible. EP 129807 describes a heat waving process in which an amino acid free of a mercapto group is used in conjunction with an alkali, e.g., tris(hydroxymethyl)amino methane. According to EP ""807 a reducing agent is not used in the disclosed heat waving process.
The heat waving method for permanent waving of hair has been replaced by the popular cold waving process, which restores the disulfide bonds as herein described. This technique for permanent waving uses chemical compounds that are capable of breaking the disulfide bonds and reshaping the hair without the provision of heat.
In cold waving, permanent waving is accomplished by a process that requires (a) chemically cleaving the disulfide bonds in hair with a reducing agent, (b) optionally rinsing the hair after cleaving the disulfide bonds, and (c) forming new disulfide bonds with an oxidizing agent while the hair is under tension in the new shape that is desired. The cold waving process is gentler to the hair than the heat waving process because the initial damage to the hair is largely reversible.
A lasting permanent wave can be achieved when the disulfide bonds are arranged in a new configuration. To reshape the hair, it is believed that 20% to 60% of the disulfide bonds must be broken and reconfigured in the new shape.
As stated previously, the reducing agent is used to break the disulfide bonds. Selection of a reducing agent is largely dependent upon the pH of the permanent cold waving composition. Generally, acidic cold permanent wave compositions employ reducing agents, such as glycerol monothioglycolate or bisulfates, and work in the lower pH range. On the other hand, cold alkaline permanent wave compositions utilize alkaline salts of thioglycolic acid. The reducing agent penetrates and swells the hair shaft thus enabling the disulfide bonds to be broken. In the cold waving process, a thiol compound, also known as a mercaptan, is typically used as the reducing agent.
Traditionally, ammonia and monoethanolamine have been used as alkalizers. However, there are drawbacks associated with these compounds. Ammonia performs well, but has a strong, irritating odor, which makes it unpleasant. Monoethanolamine has less of an odor and is commonly used as a substitute for ammonia. However, its pKa value is 9.50. This means that in a composition having a pH of 7.5, there is only one percent free amine. Thus, monoethanolamine is not as effective in such a composition. In the practice of cold waving, low heat is sometimes applied while the reducing agent is present on the hair. This accelerates the rate of cleaving of the disulfide bonds. When low heat is used, temperatures are generally less than about 50xc2x0 C. during this step, usually below 30xc2x0 C., but greater than room temperature.
One drawback to cold waving is the actual permanence of the change in shape of the hair. The newly configured hair tends to lose its shape when subject to normal stresses such as brushing, shampooing, and drying of the hair. These normal wear and tear stresses weaken the new disulfide bonds, which are constantly placed under tension.
Another drawback is the efficiency of the permanent wave. Efficiency has been characterized in the art as the tightness of the curl or xe2x80x9ctrue to rod size.xe2x80x9d Although ammonia is effective at low pH, it has a strong harsh odor. Monoethanolamine can be used as a substitute, which has a more acceptable odor, but is less efficient at low pH.
It is an object of the present invention to provide a hair treatment composition that increases the longevity of a cold permanent wave.
It is another object of the present invention to provide such a hair treatment composition that increases the efficiency of a cold permanent wave.
It is also an object of the present invention to provide such a hair treatment composition that has a pH from about 6 to about 10.
It is another object of the present invention to provide a hair treatment composition that has a high percentage of free amine in the pH range of about 6.5 to about 9.5.
It is still another object of the present invention to provide such a hair treatment composition that exhibits a n acceptable odor.
These objects and advantages are achieved by the present invention, which is a hair treatment composition for cold permanent hair waving comprising tris(hydroxymethyl)aminomethane and a reducing agent.
An essential component in the present hair treatment composition for cold permanent waving is tris(hydroxymethyl)amino methane (xe2x80x9cTrisxe2x80x9d), also known as tromethane. Tris serves as an alkalizer in the present composition. This compound has the structure shown in formula (I): 
Tris is present in an amount from about 0.2 percentage by weight or weight percent (wt. %) to about 10 wt. % of the total weight of the present permanent waving composition. Cost considerations make levels above 10 wt. % undesirable. Preferably, Tris is present in an amount from about 0.5 wt. % to about 5 wt. % of the present composition.
The pKa of Tris is about 8.06. At a pH of about 7.5. Tris has about 22% free amine, which is significantly greater than monoethanolamine. In fact, monoethanolamine has only 1% free amine available at the same pH. This is a critical point because a higher percentage of free amine (a) increases the diffusion of the amine into the hair and provides a greater number of reactive sites for the reaction between the amine and the reducing agent, and (b) provides a better buffering system to hold the pH at the desired level.
The second essential component of the present hair treatment composition for cold permanent waving is a reducing agent. Any suitable reducing agent can be used. Such suitable reducing agents include, but are not limited to thiols (mercaptans), inorganic sulfides, sulfites, hydrosulfites, phosphines, cyanides, and combinations thereof. The preferred reducing agent is a thiol or sulfite compound.
In general, any suitable thiol compound that can be used in a permanent waving composition may be employed. Preferred thiols include, but are not limited to, glycerol monothioglycolate, cysteamine, thioglycolic acid and salts of thioglycolate acid, ammonium thioglycolate, monoethanolamine thioglycolate, cysteine thioglycolate, cysteine, thiolactic acid and its salts, iso-octyl thioglycolate, N-acetyl-L-cysteine, and combinations thereof.
The pKa of a particular reducing agent is important because it greatly affects the rate at which chemical equilibrium of the reducing reaction is reached. In the present composition, the pKa of the reducing agent is about 6 to about 10. Preferably, the pKa is about 6.5 to about 9.5, more preferably about 7 to about 9.
The reducing agent is present in the present composition in an amount from about 2 wt. % to about 30 wt. % of the total composition. Preferably, the reducing agent is about 5 wt. % to about 20 wt. % of the total weight of the permanent wave composition. More preferably, there is about 8 wt. % to about 15 wt. % of the reducing agent in the present composition. The actual amount of the reducing agent that is included is determined by the waving efficiency desired.
The present composition may also have other components or additives. The additives may include, for example, one or more swelling agents such as urea, diammonium dithiodiglycolate, other alkalizers, chelating agents, fragrances, dyes, opacifiers, pearlescing agents, thickeners, wetting and foaming agents, foam stabilizers, preservatives, softening agents, surfactants, acids, buffers, solvents, conditioners, and mixtures thereof.
Suitable materials for these purposes are identified in the International Cosmetic Ingredient Dictionary and Handbook (published by The Cosmetic, Toiletry and Fragrance Association)(Eighth Edition 2000). These materials may be included in the composition at concentrations effective to provide their intended function as commonly known in the art.
By including diammonium dithioglycolate in the permanent waving composition of the present invention, greater flexibility in processing time is gained, because it minimizes the possibility of overprocessing. That is, diammonium dithioglycolate forms an equilibrium reaction with the thiol reducing agent and with cysteine in the hair keratin, which proceeds to a certain point and thus minimizes the possibility of overprocessing the hair.
Examples of other alkalizers include, but are not limited to, ammonium hydroxide, ammonium carbonate, ammonium bicarbonate, ammonium chloride, monoethanolamine, and combinations thereof.
Chelating agents that bind metal ions in solution may be included in the present composition. Examples of these chelating agents are ethylene diamine tetraacetic acid (EDTA) and its derivatives such as tetrasodium EDTA, and 1-hydroxyethylene-(1,1 diphosphonic acid) sold under the tradename Dequest 2010(copyright) by Solutia.
Wetting and foaming agents can also be included in the composition to improve penetration of the composition into the hair thereby enhancing thiol diffusion. Examples include, but are not limited to conditioners such as quaternized fatty amines or silicones.
Opacifiers can be included in the composition to provide a milky appearance. Emulsions of acrylic, vinyl, and styrene polymers and copolymers are some examples of opacifiers that are suitable.
In a preferred embodiment, the hair treatment composition has an amount from about 0.2 wt. % to about 5 wt. % tris(hydroxymethyl)amino methane and from about 8 wt. % to about 15 wt. % of a thiol compound. The pH of this preferred composition is about 6.5 to about 9.5. Preferably, the pH is about 7.0 to about 8.5. More preferably, the pH is about 7.5 to about 8.0.
Optionally, tris(hydroxymethyl)amino methane may be combined with ammonia, monoethanolamine, or combinations thereof.
The present invention includes a cold permanent waving process comprising the steps of (a) applying to hair a permanent waving composition comprising tris(hydroxymethyl)amino methane and a reducing agent, (b) allowing the permanent waving composition to set for a sufficient time, (c) removing the permanent waving composition from the hair, and (d) applying a restoring agent selected from the group consisting of oxidizing agents, crosslinking agents, and mixtures thereof to the hair. Optionally, the cold waving process may further comprise step (e) shaping the hair, prior to step (a) or after steps (b) or (c). Preferably, removing step (c) is performed by rinsing with water. Optionally, low heat may be applied during step (b), e.g., heated air at a temperature generally less than 50xc2x0 C., usually less than below 30xc2x0 C.
In the cold permanent waving process, the permanent waving composition is typically applied as a lotion, cream, or gel, after the hair has been shampooed. The hair may be reconfigured into its new shape prior to or after applying the permanent waving composition. Next, the permanent waving composition is allowed to remain on the hair for a sufficient amount of time to break a sufficient number of disulfide bonds. This may require 1 minute to 60 minutes of contact time, typically from about 10 to about 30 minutes. Low heat, e.g., from a hood style dryer, may be applied if necessary and as described previously. The permanent wave composition is then removed from the hair. Generally, this entails thoroughly rinsing the hair with water. Then, the disulfide bonds are restored. This step is essential to increase the tensile strength of the hair. Oxidizing agents typically employed include, but are not limited to, hydrogen peroxide and bromates. Crosslinking agents that are suitable include, but are not limited to alkylene dihalides, dihalocarboxylic acids, dimaleimides, and the like.
To illustrate the present invention, the following examples are provided. However, it should be understood that the present invention is not limited to the examples described.